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. Author manuscript; available in PMC: 2015 Dec 15.
Published in final edited form as: Biol Psychiatry. 2014 May 6;76(12):927–936. doi: 10.1016/j.biopsych.2014.04.014

Figure 2. Helpless rats show selective decrease in dopamine neuron population activity that is reversed by repeated injections of ketamine.

Figure 2

A) Number of spontaneously active DA neurons per electrode track. Only helpless rats showed a 50% decrease in number of active DA neurons (white bar) which was reversed by ketamine, 20 minutes post injection (red bar). Two hours after the injection, a significant increase in the population activity of non-helpless and helpless rats is observd (striped bar). In contrast, there was no change in firing rate (B) and burst firing (C) between helpless and non-helpless rats; ketamine administration 20 minutes prior recordings produced its typical increase in DA neuron rate and bursting in both groups, which is not seen 2 hours after the injection (striped bar). (D) Helpless rats show a decreased number of spontaneously active DA neurons located in the central (C) but not in the medial and lateral tracks in the VTA (white squares) compared to controls (black squares), non-helpless rats, and helpless rats treated with ketamine 20 minutes before recordings. Ketamine two hours post-injection induces an increase in population activity in the medial tracks. *p<0.05, ***p<0.001, error bars are ± SEM.

Red and brown bars represent data with injection of ketamine.